The machine, which resembles a headless pack mule made of metal, came about through a $32 million, two-and-a-half year contract between the Pentagon's research arm, known as the Defense Advanced Research Projects Agency, and Google Inc.'s Boston Dynamics, of Waltham, Massachusetts.

The robotic mule, also known as AlphaDog or LS3, was created by Alphabet-owned Boston Dynamics under a contract with DARPA. It has proved too loud to fight alongside the US Marines. Following an extended test period during the "Rim of the Pacific" military exercise last year, the project has been suspended.

The Legged Squad Support System (LS3) was created to carry heavy equipment for the Marines during marches, bearing a load of up to 400 pounds (180kg). This would have provided much-needed relief for the fighters: the average soldier is supposed to carry no more than 72 pounds (32kg) when marching and 48 pounds (22kg) when fighting, but paratroopers fighting in Iraq in 2003 carried up to 101 pounds (46kg). In total, about $42 million (£28 million) was awarded to Boston Dynamics to develop the robodog.